The aim of the work described in this thesis is to design, build, and test an active, chatter suppression system for use on a lathe. Many methods have been developed to minimise the effects of regenerative chatter in machine tools. These include machine redesign and stiffening, the inclusion of additional damping, and the use of passive and active control systems. The method described here is a development of two of these active methods, those of Comstock and Nachtigal, which control the relative position of the cutting tool. An on-line digital computer is used to monitor the cutting force, predict the relative tool-workpiece displacement, and drive the tool to suppress chatter build-up. The work is described in five main sections. After the introductary section, in which the problem is outlined and past work discussed, a theoretical analysis of chattering and its suppression is presented. Digital simulation is used to confirm and expand the theoretical results. The basic on-line identification method used to investigate the machine-workpiece structure is also presented. The third section describes the design and implementation of the experimental rigg especially the computer system and the tool positioner. Its use as a driver for a cheap, bolt-on CNC turning system is also discussed. The fourth section details the experimental work including calibration, cutting tests, suppressor validation and testing. Finally, the theory, simulation and experiments are discussed and related to past work. Suggestions are made for further reearch and development, including other applications of the system. Conclusions are drawn about the various techniques used during the work, with comments on the effectiveness of the suppression method.

The Focused Ion Beam (FIB) milling of single crystal diamond was investigated and the beam drift and mill yield were quantified. The effect of water assistance on the milling of diamond was found to double the yield. The surface morphology that spontaneously forms during milling was measured and the mechanisms behind its formation investigated. The effect of gallium implantation on the diamond crystal structure was measured by x-ray diffraction. Chemical vapour deposited polycrystalline diamond (PCD) has been machined into micro scale turning tools using a combination of laser processing and FIB machining. Laser processing was used to machine PCD into rounded tool blanks and then the FIB was used to produce sharp cutting edges. This combines the volume removal ability of the laser with the small volume but high precision ability of the FIB. Turning tools with cutting edges of 39µm and 13µm were produced and tested by machining micro channels into oxygen free high conductivity copper (OFHCC). The best surface quality achieved was 28nm Sq. This is compared to a Sq of 69nm for a commercial PCD tool tested under the same circumstances. The 28nm roughness compares well to other published work that has reported a Ra of 20nm when machining OFHCC with single crystal diamond tools produced by FIB machining. The time taken to FIB machine a turning tool from a lasered blank was approximately 6.5 hours. Improvements to the machining process and set up have been suggested that should reduce this to ~1 hour, making this a more cost effective process. PCD tools with sinusoidal cutting prongs were produced using FIB. The dimensions of the prongs were less than 10µm. The tools were tested in OFHCC and the prongs survived intact. Changes to the machining conditions are suggested for improved replication of the prongs into metal. Sapphire was FIB machined to produce nano and micro patterns on a curved surface. The sapphire is part of a micro injection mould for replication of polymer parts. The comparative economics of hot embossing and injection moulding have been studied. Injection moulding was found to be the more cost effective process for making polymer parts at commercial production levels.

Cutting tools play an important part in today's manufacturing industry. There is an ever-increasing pressure on the cutting tool design industry to produce better quality products in response to the needs of the automotive and aerospace industries. Add to this the increasing complexity of the machined product requiring the use of non-standard cutting tools. The consideration of this area of cutting tool design is in recognition of the importance of the information and knowledge requirements at the beginning and during the design process. It has been noticed that in the cutting tool industry that the knowledge provision lacks structure and organisation. Understanding the knowledge requirements of the designers would provide substantial benefits to the design process. Thus, this research explores the role and extent of special purpose cutting tool design knowledge. Literature review shows there is a lack of research examining the knowledge of designers within special purpose cutting tool design. The design of a special purpose-cutting tool is a knowledge intensive task. This thesis presents a novel methodology for Knowledge Elicitation called Knowledge = Expert - Novice (KEN). KEN is a methodology requiring active participation in the design task. It is demonstrated that KEN is suitable for the capture of cutting tool design knowledge. KEN is used to examine the nature and extent of special purpose cutting tool design. It is observed that KEN provides a structured approach to the Knowledge Elicitation from an expert. An in-depth investigation of the preliminary design stage has revealed the knowledge required by special purpose cutting tool designers. This thesis presents an ontology-based framework for cutting tool design knowledge representation following a functional, structural and behavioural methodology. The knowledge is represented by base-functions, ways of achievement and design considerations organised into functional hierarchies. The ontology is validated by domain experts rating the terms within the ontology and by cases. It is observed that the ontology is a complete representation of the cutting tool design knowledge. A viewpoint of design reuse is modelled to include a set of descriptor terms and captured domain knowledge. The viewpoint is mapped onto the ontology to provide a set of generic terms. The reuse viewpoint is then implemented onto Case-Based Reasoning software to search for past designs. The reuse viewpoint is then validated using a number of case studies and user trials. It is demonstrated that the reuse viewpoint is effective for the extraction of terms from design documentation, searching for and recalling past designs.

This research considers the temperatures generated in the workpiece during profile and cylindrical traverse grinding in the High Efficiency Deep Grinding (HEDG) regime. The HEDG regime takes large depths of cut at high wheel and workpiece speeds to create a highly efficient material removal process. This aggressive processing generates high temperatures in the contact zone between the wheel and workpiece. However, the beneficial contact angle and the rapid removal of the heated wheel – workpiece contact zone results in low temperatures in the finished surface. Temperatures in the ground surface can be predicted with knowledge of the specific grinding energy and the grinding parameters used. Specific grinding energies recorded at high specific material removal rates demonstrated a constant value of specific grinding energy dependent on cutting and contact conditions, improving accuracy of the predictive model. This was combined with a new approach to burn threshold modelling, which demonstrated an improved division of damaged and undamaged surfaces. Cutting and contact conditions in the grinding profile vary dependent on their position. This thesis shows how temperatures vary with location and estimates the partitioning of the heat flux to the regions of the grinding profile. This suggested a constant partitioning of energy to each of the three surfaces considered independently of specific material removal rates. Further a potential link was shown between the surface and the sidewall of the grinding profile, which allows temperatures in a secondary surface to be predicted given knowledge of that in the primary. Finally, the work has demonstrated the feasibility of the Superabrasive Turning process. Using small values of feed per turn and high workpiece feedrates promoted high values of removal rate with low depths of thermal penetration in the as ground surface. Thus the process has become viable for high speed cylindrical traverse grinding.

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High productivity, low cost and high profits are important issues in aerospace, automotive and tool/die metal manufacturing industries. Machining processes are widely used in manufacturing operations for metal manufacturing rather than casting and forming. However, the dynamic deflection of tool and workpiece systems generates unstable cutting forces when machining with high material removal rate. Here, sudden large vibration amplitudes occur when energy input exceeds the energy dissipated from the system, leading to self-excited vibration or chatter. This thesis focuses on the avoidance of milling chatter by using variable helix milling tools. Since milling chatter is strongly influenced by the frequency response function of the dynamic system, a preliminary study is first presented to assess the feasibility of non-contacting electromagnetic modal analysis for milling tools. It is shown that this approach shows some promise for use in real machining problems where traditional modal hammers have some drawbacks. In particular, the amplitude dependency of the frequency response function could be qualitatively illustrated. The main focus of this thesis is the optimisation of variable helix tool geometry for improved chatter performance. A semi-discretisation method was combined with Differential Evolution to optimise variable helix end milling tools. The target was to reduce chatter and maximise performance by modifying the variable helix and variable pitch tool geometry. The performance of the optimisation routine was benchmarked against a more traditional approach, namely Sequential Quadratic Programming. Numerical studies indicated that the Differential Evolution optimisation performed much better than Sequential Quadratic Programming due to the nonlinearity of the optimisation problem. The numerical study predicted total mitigation of chatter using the optimised variable helix milling tool at a low radial immersion. However, in practice, a five-fold increase in chatter stability was obtained, compared to traditional milling tools. In addition to this practical contribution, this study has provided new insight into the experimental nonlinear dynamics of variable helix milling tools, which exhibit period-one bifurcations under certain conditions. There have been very few previous studies that have investigated variable helix milling tools. However, one previous study proposed that the so-called ‘process damping' phenomenon is particularly important for variable helix milling tools. Consequently, the final contribution of this thesis is a study of process damped milling and the influence of different tool geometries. Testing was performed for tools with different rake and relief angle, edge radius and variable helix/pitch. It was found that variable helix/pitch had the greatest influence on the process damping phenomenon.

Global manufacturing trend and competition challenge every industry to seek new manufacturing methods to improve their business processes and speed up the product development cycle [Conolly, 2004a and Knights, 2001]. Among the candidates, layer manufacturing (LM) technologies appear to be a potential solution [Plam, 2002, and Grimm, 2004]. Recent LM technologies have led to a demanding application for developing production tools to manufacture parts, known as rapid tooling (RT). Selective laser sintering (SLS) is one of the leading LM systems available today in RT to manufacture injection mould (core/cavity) inserts [Kruth, 1998, Chua, 1999, Dormal, 1999, and Grenda, 2005]. However, the current capabilities of the SLS in producing metal parts have not yet fulfil the requirements of the injection mould inserts, especially in dimensional accuracy and surface finish quality [Francis, 2002 and Dalgamo, 2001 a]. The aim of this research is to use indirect SLS and high speed machining (HSM) in developing production-quality plastic injection moulding (core/cavity) inserts. The idea is that the indirect SLS process is utilised to build a near-net-shape inserts, while HSM is then utilised to finish the inserts to production specifications. Benchmark studies have been carried out to characterise the capabilities of both SLS and HSM with reference to the typical requirements of injection mould inserts. Utilising the study results, new developments of the mould inserts have been implemented on three major industrial case studies. Their performances have been evaluated and measured by comparing them with its respective original inserts. Furthermore, a set of design rules has been derived from best practices of the case studies, and have been validated by developing a new design for each case studies inserts. The results have demonstrated that the indirect SLS process has a capability III manufacturing a near-net shape of the insert which requires further related finishing to achieve final production specifications. The insert performances in some case studies have indicated significant improvements in process productivity and energy consumption as well as economic benefits to using the inserts. Regarding the significant considerations in realising the design, a recommendation on further strategic design rules and manufacturing process are highlighted so that the development of the insert using the selected approach can be more effective and efficient. Moreover, a utilisation of computer analysis software and further durability trial is also highlighted in order to predict and evaluate the optimum overall performance.

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